Method and apparatus for encoding and decoding image by using multiple reference-based motion prediction

Abstract

Provided are a method and apparatus for encoding an image by using motion prediction and a method and apparatus for decoding an image by using motion prediction. The method of encoding an image by using motion prediction, the method includes: determining at least one candidate predictor set including at least one candidate predictor within a candidate predictor range away from a location of a current predictor in a reference frame; determining a reference predictor based on a distortion rate of hypothesis predictors determined according to the at least one candidate predictor of each of the at least one candidate predictor set; performing motion prediction with regard to a current frame by using a reference block corresponding to the reference predictor and a current block; and encoding image data including the current frame based on a result of the motion prediction.

1. A method of encoding an image by using motion prediction, the method comprising:
 determining at least one candidate predictor set including at least one candidate predictor within a candidate predictor range away from a location of a current predictor in a reference frame; 
 determining a reference predictor based on a distortion rate of hypothesis predictors determined according to the at least one candidate predictor of each of the at least one candidate predictor set; 
 performing motion prediction with regard to a current frame by using a reference block corresponding to the reference predictor and a current block; and 
 encoding image data including the current frame based on a result of the motion prediction. 
 
     
     
       2. The method of  claim 1 , wherein the determining of the reference predictor comprises:
 generating a hypothesis predictor list including the hypothesis predictors of each of the at least one candidate predictor set; and 
 determining the reference predictor based on the distortion rate of the hypothesis predictors of the hypothesis predictor list. 
 
     
     
       3. The method of  claim 2 , wherein, in the generating of the hypothesis predictor list, a hypothesis predictor of a candidate predictor set that includes a candidate predictor at the location of the current predictor is ranked higher than hypothesis predictors of candidate predictor sets that do not include the candidate predictor at the location of the current predictor on the hypothesis predictor list. 
     
     
       4. The method of  claim 2 , wherein, in the generating of the hypothesis predictor list, a hypothesis predictor of a candidate predictor set having a small number of candidate predictors is ranked higher than a hypothesis predictor of a candidate predictor set having a large number of candidate predictors. 
     
     
       5. The method of  claim 1 , wherein the encoding of the image data comprises: encoding an index of the reference predictor. 
     
     
       6. The method of  claim 1 , wherein, in the determining of the at least one candidate predictor set, the candidate predictor range comprises at least one of a first range including predictors at a location a quarter-pel unit from the location of the current predictor, a second range including predictors at a location a half-pel unit from the location of the current predictor, a third range including predictors at a location an integer-pel unit from the location of the current predictor, and a predictor at the location of the current predictor. 
     
     
       7. The method of  claim 1 , wherein, in the determining of the at least one candidate predictor set, the at least one candidate predictor set comprises a first set including a candidate predictor, a second set including two candidate predictors, and a third set including three candidate predictors within the candidate predictor range. 
     
     
       8. The method of  claim 1 , wherein the determining of the reference predictor comprises:
 for each of the at least one candidate predictor set, determining one of the hypothesis predictors as an average value of candidate predictors of said each candidate predictor set; and 
 comparing distortion rates of the hypothesis predictors and determining a hypothesis predictor having a minimum distortion rate as the reference predictor. 
 
     
     
       9. The method of  claim 1 , wherein the determining of the reference predictor comprises:
 obtaining a mean squared error (MSE) with regard to the result of the motion prediction by using each of the hypothesis predictors; and 
 comparing the MSE of each of the hypothesis predictors and determining a hypothesis predictor having a minimum MSE as the reference predictor. 
 
     
     
       10. The method of  claim 1 , wherein the determining of the at least one candidate predictor set comprises:
 determining the candidate predictor range, said candidate predictor range comprising four predictors respectively located in an up, down, left, and right direction at a predetermined distance from the location of the current predictor, and four predictors respectively located at both sides of two diagonals which pass through the location of the current predictor; and 
 determining two candidate predictors that face each other with respect to the location of the current predictor from among the candidate predictors within the determined candidate predictor range to form a same candidate predictor set. 
 
     
     
       11. The method of  claim 10 , further comprising:
 encoding information regarding the predetermined distance within the candidate predictor range and information regarding directions of the candidate predictors that form the at least one candidate predictor set. 
 
     
     
       12. A non-transitory computer-readable recoding medium having recorded thereon a program for implementing the method of encoding an image by using motion prediction of  claim 1 . 
     
     
       13. A method of decoding an image by using motion prediction, the method comprising:
 extracting image data, a motion vector, and predictor information for motion prediction from a received image datastream; 
 determining a reference predictor with regard to a current block by using the predictor information; 
 performing motion prediction with regard to a current frame by using a reference block corresponding to the reference predictor, the image data, and the motion vector; and 
 reconstructing the current frame based on a result of the motion prediction, 
 wherein the reference predictor is determined as having a minimum distortion rate from among hypothesis predictors determined using at least one candidate predictor within a candidate predictor range away from a location of a current predictor in a reference frame. 
 
     
     
       14. The method of  claim 13 , wherein the determining of the reference predictor comprises:
 extracting location information from the predictor information; and 
 determining the reference predictor to be located as indicated by the location information regarding the reference frame. 
 
     
     
       15. The method of  claim 13 , wherein the determining of the reference predictor comprises:
 extracting distance information and direction information from the predictor information; 
 determining the candidate predictor range located a predetermined distance according to the distance information from the location of the current predictor on the reference frame by using the distance information; 
 determining candidate predictors located in a direction according to the direction information within the candidate predictor range by using the direction information; and 
 determining the reference predictor having the minimum distortion rate by using the candidate predictors. 
 
     
     
       16. A non-transitory computer-readable recoding medium having recorded thereon a program for implementing the method of decoding an image by using motion prediction of  claim 13 . 
     
     
       17. An apparatus for encoding an image by using motion prediction, the apparatus comprising:
 a candidate predictor set determining unit which determines at least one candidate predictor set including at least one candidate predictor within a candidate predictor range away from a location of a current predictor in a reference frame; 
 a reference predictor determining unit which determines a reference predictor based on a distortion rate of hypothesis predictors determined according to the at least one candidate predictor of each of the at least one candidate predictor set; 
 a motion prediction performing unit which performs motion prediction with regard to a current frame by using a reference block corresponding to the reference predictor and a current block; and 
 an encoding unit which encodes image data including the current frame based on a result of the motion prediction. 
 
     
     
       18. The apparatus of  claim 17 , wherein the reference predictor determining unit generates a hypothesis predictor list including the hypothesis predictors of each of the at least one candidate predictor set, and determines the reference predictor based on the distortion rate of the hypothesis predictors of the hypothesis predictor list. 
     
     
       19. The apparatus of  claim 17 , wherein the encoding unit comprises: a predictor index encoding unit which encodes an index of the reference predictor. 
     
     
       20. The apparatus of  claim 17 , wherein, for each of the at least one candidate predictor set, the reference predictor determining unit determines one of said hypothesis predictors as an average value of candidate predictors of said each of the at least one candidate predictor set, and
 wherein the reference predictor determining unit compares distortion rates of the hypothesis predictors with regard to each of the at least one candidate predictor set, and determines a hypothesis predictor having a minimum distortion rate as the reference predictor. 
 
     
     
       21. The apparatus of  claim 17 , wherein the reference predictor determining unit obtains a mean squared error (MSE) with regard to the result of the motion prediction by using each of the hypothesis predictors, compares the MSE of each of the hypothesis predictors, and determines a hypothesis predictor having a minimum MSE as the reference predictor. 
     
     
       22. The apparatus of  claim 17 , wherein the encoding unit encodes image data including the current frame based on the result of the motion prediction, and encodes information regarding a predetermined distance indicating the candidate predictor range and information regarding directions of the at least one candidate predictor that forms the at least one candidate predictor set. 
     
     
       23. An apparatus for decoding an image by using motion prediction, the apparatus comprising:
 a data extracting unit which extracts image data, a motion vector, and predictor information for motion prediction from a received image datastream; 
 a reference predictor determining unit which determines a reference predictor with regard to a current block by using the predictor information; 
 a motion prediction performing unit which performs motion prediction with regard to a current frame by using a reference block corresponding to the reference predictor, the image data, and the motion vector; and 
 an image reconstructing unit which reconstructs the current frame based on a result of the motion prediction, 
 wherein the reference predictor is determined as having a minimum distortion rate from among hypothesis predictors determined using at least one candidate predictor within a candidate predictor range in view of a location of a current predictor in a reference frame. 
 
     
     
       24. The apparatus of  claim 23 , wherein the reference predictor determining unit extracts location information from the predictor information, and determines the reference predictor to be located as indicated by the location information regarding the reference frame. 
     
     
       25. The apparatus of  claim 23 , wherein the reference predictor determining unit extracts distance information and direction information from the predictor information, determines the candidate predictor range located a predetermined distance according to the distance information from the location of the current predictor on the reference frame by using the distance information, determines candidate predictors located in a direction according to the direction information within the candidate predictor range by using the direction information, and determines the reference predictor having the minimum distortion rate by using the candidate predictors.